This invention broadly relates to data terminal interface circuits. More particularly, this invention relates to a terminal interface circuit which permits a user to connect devices using either a RS-232 or a V.35 interface to a transmission product without detailed knowledge of the interface and strapping requirements.
Interfaces between data terminals (DTE) and data communications equipment (DCE) are typically subject to standards. Among the standards for data terminal interfaces are the RS-232 and V.35 standards which govern the electrical characteristics for interchange circuits; i.e. electrical connectors. Details of the RS-232 and V.35 standards are published respectively in Interface Between Data Terminal Equipment and Data Circuit--Terminating Equipment Employing serial Binary Data InterChange; EIA-232-D; Electronics Industries Association (1987), and CCITT Red Book, Recommendations of the V Series.
It is generally desirable for multirate data communications equipment to be compatible with both RS-232 and V.35 standards so that the DTE can receive and transmit data using either format. Thus, DCE manufacturers often provide their DCE's with both RS-232 and V.35 capabilities. However, in order to operate the DCE, the user must know whether the interface being utilized is an RS-232 or V.35, and must configure the DCE (typically by hard strapping numerous berg jumpers, throwing switches, or plugging in appropriate modules) to be compatible with the interface. Moreover, if the line to which the DCE is connected is changed from an RS-232 compatible line to a V.35 compatible line or vice versa, the user must power down the DCE, reconfigure the DCE appropriately, and then power up the DCE. Further, if the user incorrectly configures the DCE; i.e. by making the wrong hard strap selections, communications interface failure can result.